1. Technical Field
The present invention relates to bonding chips into a multi-chip package and, more particularly, to an initial bond between chips that may be reworked before a final setting process.
2. Description of the Related Art
Multi-chip modules offer advantages in obtaining improved performance by shortening the electrical communication path between and among chips. Multi-chip modules also reduce the space needed by increasing integration. However, as the number of chips on a chip carrier increases, the likelihood that a chip will fail an electrical test increases. The defective component must somehow be repaired to allow the multi-chip module to function, either by routing functionality around the defective chip or by replacing the chip entirely.
In the case of chips on organic laminates, a thermosetting underfill is used to fill the gap between the chip and organic laminate immediately after a chip is attached. This protects solder interconnects from stress and strain that is created by the thermal expansion mismatch between silicon (e.g., 2.8 ppm/° C.) and the laminate (e.g., 17 ppm/° C.). However, conventional thermosetting underfill materials are intractable and prevent chip removal and replacement if a chip should prove to be defective during testing. As a result, there is no way to integrate testing and replacement procedures with multi-chip modules that use such underfills for mechanical reinforcement, because the underfills prevent reworking the chips.